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<pre>
      SUBROUTINE <a name="SROTG.1"></a><a href="srotg.f.html#SROTG.1">SROTG</a>(SA,SB,C,S)
<span class="comment">*</span><span class="comment">     .. Scalar Arguments ..
</span>      REAL C,S,SA,SB
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Purpose
</span><span class="comment">*</span><span class="comment">  =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     construct givens plane rotation.
</span><span class="comment">*</span><span class="comment">     jack dongarra, linpack, 3/11/78.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      REAL R,ROE,SCALE,Z
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC ABS,SIGN,SQRT
<span class="comment">*</span><span class="comment">     ..
</span>      ROE = SB
      IF (ABS(SA).GT.ABS(SB)) ROE = SA
      SCALE = ABS(SA) + ABS(SB)
      IF (SCALE.NE.0.0) GO TO 10
      C = 1.0
      S = 0.0
      R = 0.0
      Z = 0.0
      GO TO 20
   10 R = SCALE*SQRT((SA/SCALE)**2+ (SB/SCALE)**2)
      R = SIGN(1.0,ROE)*R
      C = SA/R
      S = SB/R
      Z = 1.0
      IF (ABS(SA).GT.ABS(SB)) Z = S
      IF (ABS(SB).GE.ABS(SA) .AND. C.NE.0.0) Z = 1.0/C
   20 SA = R
      SB = Z
      RETURN
      END

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